Heretofore, there have been known an electric vacuum cleaner provided with a cyclone system as shown in FIG. 34 (for example, see Japanese Patent Laid Open No. 2001-104223).
The electric vacuum cleaner is provided with a dust cup 1 whose upper part is opened and a motor fan 2 for causing inside of the dust cup 1 to be negatively pressured or the like. An intake vent 3 is formed at a peripheral wall 1A of the dust cup 1 and the intake vent 3 is communicated with a suction opening body 4 for sucking a dust through an intake passage 5.
The dust sucked from the suction opening body 4 is sucked inside of the dust cup 1 from the intake vent 3 of the dust cup 1 through the intake passage 5. A spiral flow is generated inside of the dust cup 1, thereby the dust and air are separated, and only the air is sucked from the upper part opening of the dust cup 1 by the motor fan 2 and is exhausted outside.
By the way, in such electric vacuum cleaner, the air sucked upwardly toward the intake passage 5 changes direction at 90 degrees and enters inside of the dust cup 1 from the intake vent 3, and at this point, the air is turned into the spiral flow and adapted to be revolved along the peripheral wall 1A of the dust cup 1 and then only the air is sucked upwardly toward the motor fan 2. Like so, because the direction of the air is changed twice, its loss of air passage is large (i.e., loss in an amount of air passing through is large), and furthermore, because the air is sucked to the motor fan 2 after revolving inside of the dust cup 1, its loss of air passage becomes exceedingly large, causing a problem that a performance of the motor fan deteriorates.
Additionally, there have been also known such a conventional electric vacuum cleaner that allows the dust which is sucked inside of a dust collection case to be separated by hitting the dust to a hyperbolic wall section as disclosed in Japanese Patent Publication No. 61-22563 for example.
In this electric vacuum cleaner, there is provided a cylindrical dust collection case that extends toward upward and downward direction, and a main body case which is loaded on a top edge of the dust collection case. Inside of the main body, the motor fan is built-in for causing a sucking-negative pressure to operate in the dust collection case.
Furthermore, in a bottom of the dust collection case, a longitudinal wall is provided which projects upwardly from a part proximity to an edge of a bottom wall. At a center of the longitudinal wall, there is formed a helical groove disengaging in an upward direction. Also, at the longitudinal wall, a partition wall is continuously built to divide inside of the dust collection case into lower side's first dust collection room and upper side's second dust collection room by marking off inside of the dust collection case into an upper part and a lower part.
The partition wall has a bottom plate whose edge has a U-shape and is also provided with a projecting portion that engages to a lower end of the helical groove of the longitudinal wall, an internal side wall which is continuously built to both sides edge of the helical groove respectively and is also built projective toward an upward direction at a part proximity to side edge in a U-shape along the side edge of the bottom plate, and a hyperbolic external side wall which is formed with a hyperbolic shape at an edge of the bottom plate corresponding to the U-shaped part of the internal wall and is also positioned opposite to the longitudinal wall. Further, at the hyperbolic part of the internal side wall, there is formed an opening, and between the internal side wall and the hyperbolic external side wall, there is formed a hyperbolic air passage.
Also, a ventilation opening is formed between the hyperbolic external wall and the longitudinal wall, and a mesh shaped filter is loaded to the ventilation opening. In addition, the hyperbolic external side wall is provided as a primary filter at the opposite side of the side wall's longitudinal wall in such a manner as to extend in upward and downward direction and roughly concentric to the dust collection case, and a hose opening is provided at the dust collection case facing the hyperbolic external side wall. Moreover, in this electric vacuum cleaner, an upper end of the dust collection case is closed with a filter holding plate, and at the filter holding plate, there is formed a tube section connected to an upper part of a hyperbolic internal side wall, and a main filter is loaded to a lower end of the tube section.
In such an electric vacuum cleaner as mentioned, when the motor fan is activated, the motor fan's sucking negative pressure acts upon the first dust collection room through the main filter, the second dust collection room and the mesh shaped filter, and the intake negative pressure that acts upon the first dust collection room acts upon the suction opening body which is not shown in the figure through dust collection hose and extension pipe for example that are connected to a hose connection opening.
By the aforementioned method, the dust sucked from the suction opening body is sucked to the first dust collection room with the air from the hose opening through the dust collection hose. And, some of the sucked dust and the air hit hyperbolic external side wall and then, flow along the hyperbolic external wall toward a side of the mesh shape filter. On this occasion, relatively heavy dust is adapted to be dropped and deposited on a bottom of a rough dust room, and remained dust's light cotton dust, for example, is captured by the mesh shaped filter when the air percolates the mesh shaped filter.
Furthermore, microscopic dust even smaller than the cotton dust passes through the mesh shaped filter together with the air. Such microscopic dust is captured through the main filter when the air passes through the main filter, and is deposited on a bottom of the second dust collection room.
But, in fact, because the air that hits the hyperbolic external side wall flows toward the side of the mesh shaped filter along the hyperbolic external side wall, the dust flows toward the side of the mesh shape filter along the hyperbolic external side wall together with the air.
In addition, relatively large and heavy dust is adapted to be deposited at a lower part of the mesh shape filter. Consequently, if an amount of dust deposited increases, then the amount of deposited dust increases at the side of the mesh shaped filter before the dust is captured in entire rough dust room, causing a tendency that the filter clogs at an early stage.
Also, because some of the air hits the hyperbolic external wall flows to the lower part along the hyperbolic external wall, the dust that hits the hyperbolic wall and drops to the lower part flows to the side of the longitudinal wall together with the air that flows to the lower part, causing some of the dust deposited on the side of the longitudinal wall to fly up, so there is a tendency that the dust flew up attaches to the mesh shaped filter and the mesh shaped filter clogs at an early stage.
The reason that these phenomena occurs is because all the air that are sucked from the hose connection opening are adapted to flow only to the first dust collection room which is to capture the dust, then adapted to flow to side of the second dust collection room through the ventilation openings' mesh shape filter which opens at the first collection room.
In addition, there is also a conventional electric vacuum cleaner in a type that loads a paper package as a paper filter at the dust collection room. In this common electric vacuum cleaner, since the intake vent, the paper package and the motor fan are arranged linearly, the loss of air passage is relatively small. However, in such common electric vacuum cleaner there is a problem that an amount of air decreases significantly once the dust accumulates in the paper package.
It is an object of the invention to provide an electric vacuum cleaner which is capable of reducing the loss of air passage, and furthermore, in which the amount of air does not decrease at the early stage even if the dust accumulates.